The present applicant proposed a product described in Japanese Patent No. 4077867 (issued date: Apr. 23, 2008) as a heat-dissipating structure that suppresses an increase in temperature caused by light absorption in a Faraday rotator used for an optical isolator. This heat-dissipating structure includes: an isolator holder within which component elements of an optical isolator main body such as a magnetic garnet crystalline film being a magnetooptical crystalline film, a polarizer, and a magnet are arranged respectively; an external heat conducting cover member covering this isolator holder; first and second heat conductive members provided within the above-described isolator holder; and flexible radiation fins formed at a part of the second heat conductive members. The above-described isolator holder is formed in a pipe shape made of a stainless steel, or the like, and has guide openings for radiation fins, which are opened toward the above-described external heat conducting cover member, formed in an upper portion thereof. The above-described external heat conducting cover member is made of copper or the like, and has an extracting opening for radiation fins, which is opened on the side of the above-described guide openings, formed therein. The above-described first heat conductive members each have a plate shape and are provided on both sides of the above-described magnetic garnet crystalline film with the magnetic garnet crystalline film being in the middle, and the above-described second heat conductive members each also have a plate shape, are positioned opposite to the above-described magnetic garnet crystalline film across the above-described first heat conductive members, are provided adjacently to the above-described first heat conductive members, and each have a hole for a light path. The above-described radiation fins extend laterally with a gap left relative to the above-described magnet to be extracted from the above-described guide openings to the outside of the above-described external heat conducting cover member through the extracting opening and have their outer end portions in contact with the above-described outside. Further, on the occasion of practical use, a pressure plate disposed on the upper side of the above-described external heat conducting cover member and a supporting plate disposed on the lower side thereof are used to sandwich the above-described external heat conducting cover member from the upper and lower sides, and the above-described pressure plate comes in pressure contact with upper surfaces of the outer end portions of the above-described radiation fins, and at the same time, bolts are screwed into holes in four corners of this pressure plate, and thereby the above-described pressure plate secures and fixes a contact between the outer end portions of the above-described radiation fins and bottom surfaces of outer grooves of the above-described external heat conducting cover member. Further, bolts are screwed into holes in four corners of the supporting plate, and thereby the supporting plate receives bolt-screwed forces of the four corners of the above-described pressure plate on the lower side.
Heat dissipation of the optical isolator is explained, and heat produced in the above-described magnetic garnet crystalline film is directly led to the second heat conductive members through the first heat conductive members and further led to the outside of the external heat conducting cover member by the respective radiation fins. Then, the led heat is dissipated to the outside through the radiation fins, which are out of contact with the principal parts of the heat-dissipating structure other than the isolator holder and the first and second heat conductive members, and as a result, in the optical isolator, an increase in temperature is suppressed and adverse effects caused by the heat, which are deterioration of optical characteristics and the like, are suppressed.